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| United States Patent |
6,232,431
|
|
Hosoki
|
May 15, 2001
|
Anaerobically hardenable sealing compound composition
Abstract
An anaerobic curable sealant composition is disclosed which is suitable as
a fluid gasket for use in portions to be sealed in the field of automobile
parts for example and which is superior in oil resistance and flexibility,
the flexibility being retained even in a high-temperature atmosphere.
The composition is prepared by adding core-shell fine particles consisting
of a core of a rubbery polymer and a shell of a glassy polymer to an
anaerobic curable sealant comprising a urethane (meth)acrylate prepolymer,
a radical-polymerizable monomer and an organic peroxide. It has a
repulsive force high enough to retain flexibility and sealability capable
of coping with vibrations and external stresses induced in a seal portion
and is superior in oily surface adhesion.
| Inventors:
|
Hosoki; Satoshi (Tokyo, JP)
|
| Assignee:
|
Three Bond Co., Ltd. (Tokyo, JP)
|
| Appl. No.:
|
367628 |
| Filed:
|
August 19, 1999 |
| PCT Filed:
|
February 20, 1998
|
| PCT NO:
|
PCT/JP98/00701
|
| 371 Date:
|
August 19, 1999
|
| 102(e) Date:
|
August 19, 1999
|
| PCT PUB.NO.:
|
WO98/37161 |
| PCT PUB. Date:
|
August 27, 1998 |
Foreign Application Priority Data
| Current U.S. Class: |
528/196 |
| Intern'l Class: |
C08G 064/00 |
| Field of Search: |
525/64
|
References Cited
Attorney, Agent or Firm: Dilsworth & Barrese, LLP
Claims
What is claimed is:
1. An anaerobic curable sealant composition comprising a urethane
(meth)acrylate prepolymer, a radical-polymerizable monomer, an organic
peroxide, and core-shell fine particles having a core of a rubbery polymer
and a shell of a glassy polymer.
2. An anaerobic curable sealant composition as set forth in claim 1,
wherein said urthane (meth)acrylate prepolymer is prepared by reacting an
isocyanate group-containing urethane prepolymer with an active
hydrogen-containing (meth)acryl monomer, said isocyanate group-containing
urethane prepolymer being prepared by reacting a polyol compound with a
polyisocynate compound at an excess molar ratio of isocyanate groups
relative to hydroxyl groups.
3. An anaerobic sealant composition as set forth in claim 1, wherein said
radical-polymerizable monomer is a substituted or unsubstituted alkyl
(meth)acrylate.
4. An anaerobic curable sealant composition as set forth in claim 1,
wherein said rubbery polymer which constitutes the core of said core-shell
fine particles has a glass transition point of below -10.degree. C., and
said glassy polymer which constitutes the shell of the core-shell fine
particles has a glass transition point of above 70.degree. C.
5. An anaerobic curable sealant composition as set forth in claim 4,
wherein said rubbery polymer which constitutes said core and said glassy
polymer which constitutes said shell each contain a (meth)acrylate monomer
as an essential constituent monomer.
6. An anaerobic curable sealant composition as set forth in claim 1,
wherein said core-shell fine particles are present in an amount of 0.1 to
80 parts by weight based on the total amount of 100 parts by weight of
both said urethane (meth)acrylate prepolymer and said
radical-polymerizable monomer.
Description
FIELD OF THE INVENTION
The present invention relates to an anaerobic curable sealant composition
and more particularly to an anaerobic curable sealant composition useful
as a fluid gasket for forming a seal between two surfaces of flanges which
are large in the amount of displacement. The anaerobic curable sealant
composition of the present invention is employable usefully especially as
a fluid gasket for preventing the leakage of a lubricating oil in various
industrial machines and devices such as internal combustion engines and
drive units.
PRIOR ART
Heretofore, in the fields of automobile parts, electric parts and various
mechanical parts, as a method for bonding and sealing components to be
sealed on an assembly line there has been adopted a method wherein sealing
surfaces are pressure-welded through a molded gasket or a method wherein
sealing surfaces are sealed through a fluid gasket. Particularly, as to
the latter method using a fluid gasket, an FIPG (Formed In Place Gaskets)
method, in which sealing surfaces are sealed under automatic application
of a liquid sealant using a robot or the like on an assembly line, is most
popular because of high productivity, low cost and highly reliable sealing
performance. As an FIPG there mainly is used an anaerobic gasket
containing as main components a room temperature curing type silicone
material (silicone RTV) which reacts with moisture contained in the air
and cures and a urethane (meth)acrylate which cures in a short time upon
contact with metallic surfaces after shutting out oxygen by sandwiching a
sealant in between flange surfaces. Particularly, silicone RTV is
presently in use most widely because of its high heat resistance and
excellent workability and adaptability to coated flange surfaces.
In the FIPG using silicone RTV, however, with upgrading of various oils,
including engine oil, the damage to silicone rubber caused by oils has
been becoming more and more serious and the attainment of a high
resistance to oil is now a problem to be solved.
Particularly, as to oils used in automobiles or the like, an acrylic
anaerobic curable sealant has come to be used. This sealant, because of an
acrylic type, involves the drawback that it is poor in flexibility as
compared with silicone compositions. The sealant is required to possess
flexibility sufficient to cope with vibrations and stresses in a sealing
portion including flanges or the like and also possess a repulsive force
sufficient to retain sealability. It is difficult to consider that the
acrylic anaerobic curable sealant satisfies these characteristics
required. Thus, this sealant is unsatisfactory in actual use, and it is
the actual situation that silicone RTV is used in most applications.
The flange of an oil pan is in many cases formed by combining different
materials such as iron and aluminum. Therefore, a large lateral
displacement is apt to occur at the flange surface due to a difference in
thermal expansion coefficient between both materials which is caused by a
change in temperature of the engine portion. The sealant layer is required
to exhibit a high follow-up performance for coping with such displacement.
This problem is serious especially in large-sized engines. The lateral
displacement of the flange surface can be diminished by increasing the
thickness of the gasket, but this attempt gives rise to an extremely
serious drawback that an anaerobic curing does not take place.
In view of this point, methods have been proposed to impart flexibility to
an anaerobic curable polymeric composition as an acrylic composition, such
as a method of imparting flexibility to the composition itself by using an
urethane acrylate as acryl material and a high molecular prepolymer
prepared by polymerizing a monomer which is a soft segment of, say, a
polyether in the main chain, and a method of imparting flexibility to the
entire composition by adding a plasticizer or synthetic rubber particles
such as acryl rubber or butyl rubber particles to an acryl polymerizable
compound.
However, in the case of using a soft segment-containing high-molecular
prepolymer, the flexibility of the composition is deteriorated when the
composition is used in an atmosphere held at 120.degree. C. or so, that
is, when subjected to heat history. At a portion which becomes high in
temperature the flexibility of sealant is lost with the lapse of time. In
the synthetic rubber particles-added type, although flexibility is
retained, there occurs a marked deterioration of solubility during
production, thus requiring a long time in the manufacturing process.
Moreover, if the sealant is stored in a liquid state, the rubber particles
may be precipitated or agglomerated and clogged in the nozzle of an
applicator. The use of a plasticizer gives rise to the drawback that the
plasticizer oozes out from the sealant after curing.
In the conventional anaerobic curable fluid gasket, if engine oil, auto
transmission fluid, or gear oil, is adhered to sealant bonding surfaces,
there occurs a marked deterioration of bonding force. Usually, a mold
release agent or an abrasive oil is adhered to the bonding surfaces and
therefore it is necessary to perform degreasing and washing with use of an
organic solvent or a detergent.
An anaerobic curable sealant composition is applied in an appropriate
amount to sealing surfaces of flanges or the like, and when the sealing
surfaces are clamped, an oxygen-shut out portion polymerizes and cures to
form a seal layer. However, when the amount of the composition to be
applied cannot be controlled precisely or when it is used in an excess
amount for attaining a reliable sealing performance, the composition may
be forced out from the flange surfaces. The thus-exposed portion of the
anaerobic curable sealant composition, which portion is in contact with
air, does not cure. Therefore, it is necessary that the composition should
possess a property not exerting a bad influence on the surrounding
materials.
Particularly when the anaerobic sealant composition is used in the engine
and transmission of an automobile or the like, it is required in practical
use that the composition exposed from the flange bonding surfaces and
before curing should have a property of being dispersed uniformly in the
oils used. The anaerobic curable composition containing synthetic rubber
particles as a flexibility imparting agent is deficient in such
dispersibility.
OBJECTS OF THE INVENTION
It is an object of the present invention to solve the above-mentioned
problems of the prior art and provide an anaerobic curable sealant
composition superior in all of oil resistance, flexibility and sealability
and capable of retaining excellent felxibility even after subjected to
heat history.
SUMMARY OF THE INVENTION
The present invention resides in an anaerobic curable sealant composition
comprising an urethane (meth)acrylate prepolymer, a radical polymerizable
monomer, an organic peroxide, and core-shell fine particles comprising a
core of a rubbery polymer and a shell of a glassy polymer.
DETAILED DESCRIPTION OF THE INVENTION
An anaerobic curable sealant composition comprising an urethane
(meth)acrylate prepolymer, a radical-polymerizable monomer and an organic
peroxide is already publicly known. The present invention is characterized
by adding specific fine particles to the said composition to improve the
performance of the composition.
The urethane (meth)acrylate used in the present invention is a prepolymer
having a urethane structure in its main chain and having (meth)acryloyloxy
groups at its ends. This prepolymer is prepared by reacting a compound
having two or more hydroxyl groups as functional groups with an organic
compound having two or more isocyanate groups as functional groups to
prepare a polyurethane prepolymer and introducing (meth)acryloyloxy groups
into its molecular ends.
For example, the prepolymer in question is obtained by reacting a urethane
prepolymer, which results from mixing and reacting a polyether polyol and
an organic diisocyanate at a molar ratio in the range from 1:1 to 1:2 in a
diluting solvent, with a (meth)acryl monomer having active hydrogen in an
amount sufficient to react with all of the remaining isocyanate groups in
the said urethane prepolymer. The urethane (meth)acrylate prepolymer may
be used alone, or two or more such prepolymers may be mixed together and
used. By the term "(meth)acrylate" is meant acrylate or methacrylate, and
by the term "(meth)acryloyloxy group" is meant acryloyloxy group or
methacryloyloxy group. The term "oligomer" represents a dimer or a
multimer having two or more urethane bonds, including a polymer.
As to the molecular weight of the urethane (meth)acrylate prepolymer, the
molecular weight of the resulting prepolymer can be selected freely, for
example, by adjusting the molecular weight of a compound having two or
more hydroxyl groups as functional groups such as a polyether polyol or by
adjusting the degree of reaction between a compound having two or more
hydroxyl groups as functional groups and a compound having two or more
isocyanate groups as functional groups. Usually prepared is a prepolymer
of dimer to hectomer in terms of the degree of polymerization.
As the urethane (meth)acrylate prepolymer there may be used a publicly
known one, as noted previously.
As the organic compound having two or more hydroxyl groups as functional
groups for used in preparing the urethane prepolymer there may be used any
of various aliphatic polyols and aromatic polyols. Examples are ethylene
glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, diethylene
glycol, triethylene glycol, 1,6-hexanediol, neopentyl glycol,
trimethylolpropane, glycerin, pentaerythritol, 1,2,6-hexanetriol,
hydroxylated biphenol A, polyether polyol, and polyester polyol, with
.alpha., .omega.-diols being particularly preferred.
As the compound having two or more isocyanate groups as functional groups,
which is the other component for use in preparing the urethane prepolymer,
there may be used any of various aliphatic polyisocyanates and aromatic
polyisocyanates. Examples are diphenylmethane diisocyanate, tolylene
diisocyanate, naphthalene diisocyanate, xylene diisocyanate, and
hexamethylene diisocyanate. Diisocyanates are particularly preferred.
In the reaction of the compound having two or more hydroxyl groups as
functional groups with the compund having two or more isocyanate groups as
functional groups, both compounds are used in such a manner that the
isocyanate groups of the latter compound are in a proportion of equimolar
amount or more, i.e., NCO/OH.gtoreq.1, preferably 1.about.2, more
preferably 1.1.about.1.7, relative to the hydroxyl groups of the former
compound. It is particularly preferred that isocyanate groups be present
at both ends of the urethane prepolymer.
Also as to the (meth)acryl monomer having active hydrogen for use in the
reaction with the thus-prepared urethane prepolymer having isocyanate
groups at both ends thereof, there may be used a known one. As examples of
active hydrogen sources are mentioned hydroxyl group, amino group,
carboxyl group, and mercapto group. More concrete examples include
hydroxyl-containing (meth)acrylates such as hydroxyalkyl(meth)acrylate,
mercapto-containing (meth)acryaltes such as mercaptoalkyl(meth)acrylate,
and (meth)acrylic acid. As alkyl groups are preferred those having 1 to 6
carbon atoms. The thus-exemplified (meth)acryl monomer having active
hydrogen is used in an amount sufficient to react stoichiometrically with
the isocyanate groups in the urethane polymer molecules.
The radical polymerizable monomer used in the present invention may also be
a known one. Usually employed is a radical-polymerizable monomer having
one polymerizable unsaturated bond. Particularly preferred is a
substituted or unsubstituted alkyl (meth)acrylate such as, for example, a
(substituted) alkyl (meth)acrylate wherein the alkyl moiety has 1 to 18
carbon atoms. Exampes are ethyl (meth)acrylate, n-propyl (meth)acrylate,
isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate,
n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl
(meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, n-decyl
(meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate,
2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate,
2-phenoxyethyl (meth)acrylate, stearyl (meth)acrylate, tridecyl
(meth)acrylate, 3-methoxypropyl (meth)acrylate, 3,3-methoxymethylpropyl
(meth)acrylate, 2-hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)
acrylate. These radical-polymerizable monomers may be used each alone or
as a mixture of two or more.
The radical-polymerizable monomer is used in an amount of usually 1 to 50
parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by
weight of the urethane (meth)acrylate prepolymer.
The core-shell fine particles used in the present invention are
characterized in that the core portion is constituted by a rubbery polymer
and the shell portion by a glassy polymer. The particles have "elasticity"
in the core portion and "hardness" in the shell portion and do not
dissolve in a liquid resin. The polymer which constitutes the "core"
substantially has a glass transision temperature below the ambient
temperature, while the polymer which constitutes the "shell" substantially
has a glass transition temperature above the ambient temperature. The
range of the ambient temperature is established as a temperature range in
which the sealant is used.
According to a preferred method for producing the fine particles used in
the present invention, first the core portion is produced by polymerizing
a polymerizable monomer. As the polymerizable monomer there may be used a
known monomer insofar as the monomer affords a rubbery polymer. Examples
are (meth)acrylate monomers such as n-propyl (meth)acrylate, n-butyl
(meth)acrylate, 2-ethylhexyl (meth) acrylate, and n-decyl (meth)acrylate,
aromatic vinyl compounds such as styrene, vinyltoluene, and
.alpha.-methylstyrene, vinyl cyanide compounds such as acrylonitrile and
methacrylonitrile, as well as monomers having one polymerizable
unsaturated bond such as vinylidene cyanide, 2-hydroxyethyl
(meth)acrylate, 3-hydroxybutyl (meth)acrylate, 2-hydroxyethyl fumarate,
hydroxybutyl vinyl ether, monobutyl maleate, and butoxyethyl methacrylate.
As further examples are mentioned ethylene glycol di(meth)acrylate,
butylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate,
trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate,
hexanediol tri(meth)acrylate, oligoethylene di(meth)acrylate,
oligoethylene tri(meth)acrylate, aromatic divinyl monomers such as
divinylbenzene, and crosslinkable monomers having two or more
polymerizable unsaturated groups such as triallyl trimellitate and
triallyl isocyanate. These polymerizable monomers may be used each alone
or as a mixture of two or more insofar as they afford rubbery polymers.
But the latter crosslinkable monomers are usually employed in combination
with the former compounds.
Rubber properties vary depending on the molecular weight, molecular shape
and crosslink density of the polymer prepared by polymerizing any of the
polymerizable monomers exemplified above. In the present invention it is
required that the core portion be constituted by a polymer which is
rubbery at room temperature. It is more preferable that the resulting
polymer has a glass transition point of below -10.degree. C.
Next, in the presence of the thus-prepared polymer particles as a core,
there is performed a second polymerization involving polymerizing a
polymerizable monomer to form a shell of a polymer which possesses glassy
properties at room temperature. This polymerizable monomer may be selected
from those exemplified previously as core forming monomers, provided it is
required in the present invention that the polymer which constitutes the
shell portion be glassy at room temperature. Preferably, the resulting
polymer has a glass transition point of above 70.degree. C. This can be
determined taking into account the molecular weight, molecular shape and
crosslink density of the polymer obtained by polymerizing the selected
polymerizable monomer. If the polymer which constitutes the shell portion
is not glassy at room temperature, then when the polymer particles are
mixed into the radical-polymerizable liquid resin to prepare a sealant
composition, the particles will be swollen by the radical polymerizable
monomer, and with the lapse of time during storage, its viscosity will
increase to form gels. That is, the storage stability will become low.
As preferred examples of the polymerizable monomer for forming the shell
portion there are mentioned alkyl (meth)acrylates wherein the alkyl moiety
has 1 to 4 carbon atoms, such as ethyl (meth)acrylate, n-butyl acrylate,
methyl methacrylate, and butyl methacrylate. These (meth)acrylates may be
used each alone or in combination of two or more. Among them, methyl
methacrylate is particularly preferred.
The amount of the core-shell fine particles is 0.1 to 80 parts by weight,
preferably 5 to 65 parts by weight, based on the total amount of 100 parts
by weight of the urethane (meth)acrylate oligomer and the
radical-polymerizable monomer. If the amount thereof is smaller than 0.1
part by weight, it will be difficult to let the sealant composition
exhibit excellent flexibility when cured, and an amount thereof exceeding
80 parts by weight will lead to an extreme increase of viscosity and
deterioration of the storage stability. Particularly preferred is an
amount in the range of 10 to 40 parts by weight.
By the term "anaerobic" is meant a property which dislikes air, more
particularly, a property such that stability and liquid state are retained
in the presence of air or oxygen, but in the absence of air or oxygen
there starts polymerization immediately. Anaerobic sealants have
heretofore been used for bonding and sealing metallic part and for
preventing looseness and fixing portions which are fitted together, and
are thus publicly known. It is also publicly known that an anaerobic
curable composition comprises a radical-polymerizable monomer such as a
(meth)acrylate, a prepolymer thereof, a polymerization initiator such as
an organic peroxide, a curing accelerator, and a polymerization inhibitor.
Suitable such known components, including an organic peroxide, may be used
in the present invention.
As examples of organic peroxides are mentioned such hydroperoxides as
cumene hydroperoxide, t-butyl hydroperoxide, and diisopropylbenzene
hydroperoxide, as well as diacyl peroxides, dialkyl peroxides, ketone
peroxides, and peroxy esters, with cumene hydroperoxide being particularly
preferred in point of stability and curing speed.
The amount of the organic peroxide to be used cannot be limited because it
depends on the balance among the kind of the peroxide used, curing time
and storage period, but is usually in the range of 0.01 to 10 parts by
weight, preferably 0.1 to 5 parts by weight, based on the total amount of
100 parts by weight of the urethane (meth)acrylate and the
radical-polymerizable monomer.
In order for anaerobic curing to take place effectively, it is desirable to
add a curing accelerator in addition to the organic peroxide. Examples of
curing accelerators include organic sulfone imides, amines, and
organometallic salts. As organic sulfone imides, o-benzoic sulfimides are
preferred. As amines, diethylamine, triethylamine,
N,N-dimethylparatoluidine, and 1,2,3,4-tetrahydroquinone are preferred. As
examples of organometallic salts are mentioned copper chloride and copper
octylate. Where required, there may be added accelerators such as
secondary and tertiary amines, stabilizers such as benzoquinone,
hydroquinone, and hydroquinone monomethyl ether, polymerization inhibitors
such as phenols, and chelate compounds such as ethylenediaminetetraactic
acid (EDTA), sodium salts thereof, oxalic acid, acetylacetone, and
o-aminophenols.
In the case where the flange material is an inert material such as a
plastic material or where oxygen is present due to a large clearance,
making anarobic curing difficult, it is recommended to apply a curing
accelerating primer beforehand to the flange surfaces to be bonded, the
curing accelerating primer containing a reducing agent for accelerating
the decomposition of the organic peroxide to form radicals, whereby curing
can be allowed to take place in a short time.
As the curing accelerating primer which contains a reducing agent for
accelerating the decomposition of the organic peroxide to form radicals,
it is desirable to use a primer which contains a condensate of an aldehyde
compound and a primary or secondary amine and/or an oxidizable transition
metal-containing compound. As examples of such condensate are mentioned
butylaldehyde-butylamine condensate, butylaldehyde-aniline condensate, and
acrolein-aniline condensate.
As examples of the oxidizable transition metal-containing compound are
mentioned organic compounds containing a transition metal selected from
the group consisting of iron, cobalt, nickel and manganese, with metal
chelates and complex salts being particularly useful. More concrete
examples are pentadione iron, pentadione cobalt, pentadione copper,
propylenediamine copper, ethylenediamine copper, iron naphthenate, nickel
naphthenate, cobalt naphthenate, copper naphthenate, copper octenoate,
iron hexoate, iron propionate, and acetylacetone vanadium. Substituted
thioureas such as ethylenethiourea and benzothiazole are also employable.
For preparing the primer, it is preferable that the above reducing
compounds be dissolved in a proportion of 0.05 to 10 wt % in such organic
solvents as toluene, acetone, methyl ethyl ketone, and alcohols.
Into the sealant composition of the present invention there may be added,
if necessary, various fillers such as fumed silica for the adjustment of
viscosity, plasticizers, adhesion imparting agents such as silane
compounds and phosphoric esters, and various known (meth)acrylic ester
monomers for the adjustment of rubber strength, including hardness and
elongation, such as isoborny (meth)acrylate, 2-hydroxyethyl
(meth)acrylate, and 2-hydroxypropyl (meth)acrylate.
In the anaerobic curable composition of the present invention, since fine
core-shell particles are added as a functional filler to the combination
of the urethane (meth)acrylate prepolymer and the radical-polymerizable
monomer, the flexibility of the composition does not deteriorate so
markedly even under heat history, and the core-shell fine particles can be
dispersed easily in the composition. Since the core-shell fine particles
have an oil absorbing property, the bonding force of the composition is
not deteriorated even on a surface with oil or the like adhered thereto.
The anaerobic curable composition before curing, which contains the
core-shell fine particles, is dispersed easily in oil.
EXAMPLES
For easier understanding of the present invention, the invention will be
described in detail hereinunder by way of Examples thereof, which,
however, do not restrict the scope of claim.
Preparing Sealant Compositions 1.about.6
An urethane (meth)acrylate prepolymer UN-1101T (a product of Negami Kogyo
Co.) having a polyether in the main chain thereof, an urethane
(meth)acrylate prepolymer UN-2500 (a product of Negami Kogyo Co.) having a
polyester in the main chain thereof, and an epoxy acrylate SP-1507 (a
product of Showa Kobunshi Co.), as urethane (meth)acrylate prepolymers,
phenoxyethyl acrylate as a radical-polymerizable monomer, cumene
hydroperoxide as an organic peroxide, ethylenediaminetetraacetic acid
(EDTA) and butylhydroxytoluene (BHT) as stabilizers, saccharin,
benzothiazole, n-dodecylmercaptan, and DAROCUR 1173 (a product of Ciba
Geigy Co.), as accelerators, silica as a filler, and F-351 (a product of
Nippon Zeon Co.) and STAPHYLOID IM-101 (a product of Takeda Chemical
Industries, Ltd.) as core-shell fine particles comprising a core of a
rubbery polymer and a shell of a glassy polymer, were used at such weight
ratios as shown in Table 1 to prepare compositions 1 to 6.
Preparing Sealant Compositions 7.about.12 for comparison
Compositions 7 to 12 were prepared at such weight ratios as shown in Table
2, using the compounds used in the above preparation of compositions 1 to
6, provided some of them did not use the core-shell fine particles used in
the above preparation of compositions 1 to 6, but instead used
ethylene-acryl rubber fine particles, liquid butadiene-acrylonitrile, and
bis-2-ethylhexyl phthalate (DOP) and ethylene glycol as plasticizers.
Examples 1.about.6 & Comparative Examples 1.about.6:
Heat Deterioration Test
DAROCUR 1173 as an ultraviolet curing catalyst was added to the
compositions 1.about.12, followed by radiation of ultraviolet light, to
prepare about 2 mm thick sheets, from which were fabricated No. 2 dumbbell
specimens. The specimens thus fabricated were then subjected to curing in
a circulating hot air dryer at 120.degree. C. and 150.degree. C. for 240
hours. Thereafter, the specimens were measured for percent elongation, the
results of which are set out in Table 3.
Examples 7.about.12 & Comparative Examples 7.about.12:
Oily Surface Adhesion Test
The compositions 1 to 12 were measured for oily surface bonding force under
shear. Specimens were prepared in the following manner. Bonding surfaces
of aluminum plates (A2024P)(size: 1.6.times.25.times.10 mm) defined by JIS
H4000 were polished with sand paper #240 and then washed with toluene.
Auto transmission fluid was applied about 0.5 mg/cm.sup.2 to one specimen.
Then, each of the anaerobic curable compositions 1 to 12 was applied onto
the one specimen so as to protrude upon superposition of the other
specimen thereon, and the specimens were superposed together 10 mm. Using
two clothespins, the superposed surfaces were pinched form both sides. The
rate of pulling in the shear bonding force measurement was set at 10
mm/min and the curing time was set at 72 hours. The results obtained are
shown in Table 4.
Examples 13.about.18 & Comparative Examples 13.about.18:
Oil Dispersibility Test
200 ml of auto transmission fluid was put into a 500 ml glass beaker, into
which was then added 0.2 g of each of the compositions 1 to 12, followed
by agitation for 3 hours using a handy type agitator (revolutions: 500
rpm, agitating blades: propeller type, diameter: 50 mm). After subsequent
filtration using filter paper (500 mesh), a check was made visually to see
if there was any residue. The results obtained are shown in Table 5, in
which the ".largecircle." mark stands for the absence of residue, while
the mark "X" stands for the presence of residue.
EFFECT OF THE INVENTION
The anaerobic curable composition of the present invention has flexibility
comparable to that of a silicone composition and has a repulsive force
high enough to retain flexibility and sealability capable of coping with
vibrations and stresses induced in the seal portion between flanges for
example. Thus, the follow-up performance of the sealant layer is high.
Moreover, even when the composition is used in a high-temperature
atmosphere, it is possible to retain an excellent sealability without
deterioration of flexibility.
The core-shell fine particles used in the present invention can be easily
dispersed as a functional filler in the composition, thus making it
possible to simplify the manufacturing process and reducing the
manufacturing cost.
Further, since the anaerobic curable sealant composition of the present
invention exhibits an oil absorbing action, its oily surface bonding force
is superior to that of the conventional flexibility-imparted anaerobic
curable composition. More particularly, even if a lubricating oil such as
engine oil or auto transmission fluid, or a mold release agent used in
molding, or a polishing oil or the like, is adhered to the surface to be
sealed such as a flange surface, it is not necessary to perform degreasing
and washing with use of a solvent or a detergent. Thus, the manufacturing
process can be so much simplified.
Additionally, the anaerobic curable composition before curing according to
the present invention, which contains acryl type core-shell fine
particles, is dispersed in oil without agglomeration. Therefore, when the
composition is used for sealing flange surfaces in an automobile engine or
transmission, there is no fear that the portion of the composition
protruded to the exterior from the flange surfaces may exert a bad
influence on various oils. But the protruded portion will be dispersed
uniformly in the oils.
TABLE 1
Composition
Components 1 2 3 4 5 6
polyether-based urethane 200.0 200.0 200.0
acrylate prepolymer
polyester-based urethane 200.0 200.0 200.0
acrylate prepolymer
phenoxyethyl acrylate 50.0 50.0 50.0 50.0 50.0 50.0
EDTA stabilizer 0.4 0.4 0.4 0.4 0.4 0.4
BHT 0.5 0.5 0.5 0.5 0.5 0.5
Saccharin 2.5 2.5 2.5 2.5 2.5 2.5
benzothiazole 1.2 1.2 1.2 1.2 1.2 1.2
n-dodecylmercaptan 1.0 1.0 1.0 1.0 1.0 1.0
cumene hydroperoxide 5.0 5.0 5.0 5.0 5.0 5.0
silica 8.0 8.0 8.0 8.0 8.0 8.0
core-shell rubber (1) 20.0 5.0 30.0 65.0
core-shell rubber (2) 30.0
core-shell rubber (3) 30.0
TABLE 2
Composition
Components 7 8 9 10 11 12
polyether-based urethane 200.0 200.0 200.0 200.0 200.0
acrylate prepolymer
epoxy acrylate 200.0
phenoxyethyl acrylate 50.0 50.0 50.0 50.0 50.0 50.0
EDTA stabilizer 0.4 0.4 0.4 0.4 0.4 0.4
BHT 0.5 0.5 0.5 0.5 0.5 0.5
saccharin 2.5 2.5 2.5 2.5 2.5 2.5
benzothiazole 1.2 1.2 1.2 1.2 1.2 1.2
n-dodecylmercaptan 1.0 1.0 1.0 1.0 1.0 1.0
cumen hydroperoxide 5.0 5.0 5.0 5.0 5.0 5.0
silica 8.0 8.0 8.0 8.0 8.0 8.0
core-shell rubber (1) 30.0
ethylene-acryl rubber 20.0 20.0
liquid butadiene- 20.0
acrylonitrile
DOP 10.0
ethylene glycol 30.0
TABLE 3
Example/ Percent elongation
Comparative Composition after 120.degree. C. after
150.degree. C.
Example used Initially heat history heat history
Ex. 1 composition 1 138 127 110
Ex. 2 composition 2 135 119 95
Ex. 3 composition 3 141 126 114
Ex. 4 composition 4 185 180 165
Ex. 5 composition 5 170 160 128
Ex. 6 composition 6 153 127 110
Com.Ex. 1 composition 7 120 100 75
Com.Ex. 2 composition 8 150 142 118
Com.Ex. 3 composition 9 156 149 121
Com.Ex. 4 composition 10 145 120 93
Com.Ex. 5 composition 11 50 15 9
Com.Ex. 6 composition 12 190 180 161
TABLE 4
Oily Surface Adhesion Test
Example/ Shear Bonding Force
Comparative oily degreased
Example Composition used surface surface
Ex. 7 Composition 1 2.2 4.5
Ex. 8 Composition 2 2.6 5.1
Ex. 9 Composition 3 2.5 4.8
Ex. 10 Composition 4 3.2 4.0
Ex. 11 Composition 5 1.7 3.2
Ex. 12 Composition 6 1.8 3.4
Com.Ex. 7 Composition 7 0.9 6.0
Com.Ex. 8 Composition 8 0.8 3.2
Com.Ex. 9 Composition 9 0.6 3.4
Com.Ex. 10 Composition 10 0.5 4.3
Com.Ex. 11 Composition 11 1.8 7.6
Com.Ex. 12 Composition 12 0.5 2.2
TABLE 5
Oil Dispersibility Test
Example/
Comparative
Example Composition used Evaluation
Ex. 13 Composition 1 .smallcircle.
Ex. 14 Composition 2 .smallcircle.
Ex. 15 Composition 3 .smallcircle.
Ex. 16 Composition 4 .smallcircle.
Ex. 17 Composition 5 .smallcircle.
Ex. 18 Composition 6 .smallcircle.
Com.Ex. 13 Composition 7 .smallcircle.
Com.Ex. 14 Composition 8 X
Com.Ex. 15 Composition 9 X
Com.Ex. 16 Composition 10 .smallcircle.
Com.Ex. 17 Composition 11 .smallcircle.
Com.Ex. 18 Composition 12 X
Note)
".smallcircle." stands for the absence of residue.
"X" stands for the presence of residue.
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